All Basic Knowledge About Fiber Optic Cable

As a light transmission tool, optical fiber has been widely used in engineering projects because of its faster transmission rate, more stable signal, higher safety factor, and more environmental protection. Fiber optic cable is a communication cable assembly that uses one or more optical fibers placed in a sheath as the transmission medium and can be used individually or in groups. How much do you know about optical fibers and optical cables in daily projects?

Briefly describe the composition of optical fiber?

Answer: Optical fiber consists of two basic parts: a core made of transparent optical materials and a cladding and coating layer.

What are the basic parameters that describe the transmission characteristics of optical fiber lines?

Fiber mainly parameters to decide the quality is the Including loss, dispersion, bandwidth, cut-off wavelength, mode field diameter, etc.

What are the causes of fiber attenuation?

The attenuation of optical fiber refers to the reduction of optical power between two cross-sections of an optical fiber, which is related to the wavelength. The main causes of attenuation are scattering, absorption and optical loss caused by connectors and joints.

How is the fiber attenuation coefficient defined?

It is defined by the attenuation (dB/km) of a uniform optical fiber per unit length in the steady state.

What is insertion loss?

Insertion loss refers to the attenuation caused by the insertion of optical components (such as connectors or couplers / adapters ) into optical transmission lines.

What is the bandwidth of optical fiber?

The bandwidth of optical fiber refers to the modulation frequency when the amplitude of optical power is reduced by 50% or 3dB from the amplitude of zero frequency in the transfer function of optical fiber. The bandwidth of an optical fiber is approximately inversely proportional to its length, and the product of the bandwidth length is a constant.

What impact will the dispersion of optical fiber have on the performance of optical fiber communication system?

The dispersion of optical fiber will cause the light pulse to broaden during transmission in the optical fiber. It affects the bit error rate, the length of the transmission distance, and the system rate.

The phenomenon of light pulse broadening in optical fibers caused by different group velocities of different wavelengths in the spectral components of the light source.

light pulse

What are the types of dispersion in optical fiber? What is it related to?

The dispersion of optical fiber refers to the broadening of the group delay in an optical fiber, including mode dispersion, material dispersion and structural dispersion. Depends on the characteristics of both the light source and the optical fiber.

How to describe the dispersion characteristics of signals propagating in optical fibers?

It can be described by three physical quantities: pulse broadening, fiber bandwidth, and fiber dispersion coefficient.

What is the cut-off wavelength?

It refers to the shortest wavelength that can only transmit the fundamental mode in the optical fiber. For single-mode fiber, its cutoff wavelength must be shorter than the wavelength of the transmitted light.

What are the most common optical cable structures?

There are two types: layered type and skeleton type.

What does an optical cable mainly consist of?

Optical cables are mainly composed of fiber core, fiber optic grease, sheath materials, PBT (polybutylene terephthalate) and other materials.

What does the armoring of optical cables mean?

The armor of optical cables refers to the protective elements (usually steel wires or steel strips) used in special-purpose optical cables (such as submarine optical cables, etc.). The armor is attached to the inner jacket of the fiber optic cable.

Armored fiber optic cable

What material is used for optical cable sheath?

Optical cable jackets or sheaths are usually made of polyethylene (PE) and polyvinyl chloride (PVC) materials, and their function is to protect the cable core from external influences.

PVC

What kind of optical cables used in power systems?

There are mainly three types of special optical cables in power systems:

Optical fiber ground composite cable (OPGW), the optical fiber is placed in the power line of the steel-clad aluminum strand structure. The application of OPGW optical cable plays the dual functions of ground wire and communication, effectively improving the utilization rate of power towers.

Wrap-around optical cable (GWWOP), which is wound or suspended on the ground wire where there are existing power transmission lines.

Self-supporting optical cable (ADSS) has strong tensile strength and can be hung directly between two power towers, with a maximum span of up to 1000m.

What are the technical conditions that need to meet when choose an OPGW cable?

  • 1) Nominal tensile strength (RTS) of OPGW optical cable (kN);
  • 2) Number of optical fiber cores (SM) of OPGW optical cable;
  • 3) Short circuit current (kA);
  • 4) Short circuit time (s);
  • 5) Temperature range (℃).

What are the application structures of OPGW optical cable? 

OPGW cable

There are 6 main types of institutions:

  • 1) Structure of plastic pipe layer stranding + aluminum pipe;
  • 2) Structure of central plastic tube + aluminum tube;
  • 3) Aluminum frame structure;
  • 4) Spiral aluminum tube structure;
  • 5) Single-layer stainless steel tube structure (center stainless steel tube structure, stainless steel tube layer twisted structure);
  • 6) Composite stainless steel tube structure (center stainless steel tube structure, stainless steel tube layered structure).

What are the main materials of the stranded wire outside the OPGW optical cable core?

It is composed of AA wire (aluminum alloy wire) and AS wire (aluminum clad steel wire).

How is the bending degree of optical cable limited?

The bending radius of the optical cable should be no less than 20 times the outer diameter of the optical cable, and not less than 30 times the outer diameter of the optical cable during construction (non-stationary state).

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